Directive antenna system



Dec. 5, 1944. A. D. MARTIN, JRv

DIRECTIVE ANTENNA SYSTEM Filed Aug. 6, 1941 2 Sheets-Sheet 1 Dec. 5, 1944. A, D, MARTlN, JR 2,364,084

DIRECTIVE ANTENNA SYSTEM Filed Aug. 6, 1941 2 Sheets-Sheet 2 Patented Dec. 5, 1944 i i UNITED STATES PATENT lOFIFlCE e DIRECTIVE ANTENNA SYSTEM e, Albert D. Martin, Jr., Washington, D. 1C. Application August c, 1941,fseria1No. :405,676

reclaim. wieso-.1n

" (Granted `under the lact of March 3, 1883, :as amended April'30,"1928; 3700. u757) The invention described herein may be manulfa'ctured and used by or for the Government `for `,governmental purposes, Awithout the payment lto me of any royalty thereon.

'This invention relates te radio `antennas and more `particularly tot directive `transmitting `ari-- Atennas for radio marker facilities for air `naviga'- tion. 'The invention has for its primary object Ithe provision of an antenna that is more rugged in design, .is simpler to adjust, is more efficient in 'operation and has a more `conned'field pattern 4than prior antennas of this general character.

`Briefly speaking, the primary features `of my' invention comprise two half wavelength radiating elements mounted at right angles with-comthe radiation diminishing man inverse relation `Whenthe ele-g with the angle from said normal.

less, 'from theplane of the" radiating elements. It may comprise 'asheet of metal or of wiremesh. The `dimensions of the reflecting plane are relatively 'large in comparison with one wavelength.

The feeders I5, I6, I1, and I 8- are symmetrically -located with respect to the supporting member "4I, respectively'iconverging slightly `from the radiating elements `to the insulating bushings 45, '43, 41I, and `42 in the 'reflecting plane 39 `and respectively extending thence with constant spacing 'to-conveniently located anchors 4S, ljlli, and 41. Feeders I5 and IIS are respectively connected to feeders 4I1-and 'I"8 bymeans of 4jumpers ments and reecting plane are horizontal, the

radiated field pattern is particularly well suited for use asa marker for the navigationr-ofaircraft. .'Otherobjects andfeatures ofconstructionwill becomeapparent `as this description proceeds.

With Yreference to the drawings, Fig. `l is la perspective View of one form Lof the antenna sys- Atem constituting my invention.4 Fig. 2 is a side YI6. Likewise, II and I3 constitute a second and similar element oriented ninety degrees from the rst and driven by feeders VII and I8. The two.`

radiating elements are mechanically..supported by a metallic hub Il)` and a rodor :pipe'member` 4I. The lengths'of the vradiating kelements "and the points of connection Aof the feedersth'ereto -are adjustable to facilitate thetuning operations. `The horizontal reflecting plane i39-is lparallel 'to fandspaced preferablytonequarterlwavelengtm for "32 and 33. Jumpers BIiand `3'I are situatedone quarters wavelenth (from jumpers 32 and V33. Radio frequency power'is applied tothe system` at pointsIiS and 20 through feeders 23 ancl2 and'matching' section 2I and 22 which are mechanically anchored at points 21 and 'fthrough conductors 25and 28. Jumper`29 issituated one l quarter 'wavelength from vpoints I9 and 20.

Reference is made to lFig.` 4 for aclear`under` standing-of the'operation of this antenna system. The transmission line comprising 4feeders `I5 and IIB is "terminated in 'its `clfiar'acteristic impedance in the radiating `element vI2, I4. Likewise "the transmissioniline'comprising feeders `I 'I and I8 'is terminated infits characteristic impedance in the radiatingelementfI-l, I3. The two transmission lines `are `e'iectively connected in parallel at points ISand `2`I); however, feeders I1 and I8 `are each madelonger than feeders I5 and IIby one qua-rterwavelength by adjusting theposition'of jumpers 32 and 33. Consequently v4when radio frequency 'power is yapplied between points I9 'and 20,th'e radiating elements I2, I4, and 4'I I, I3 i are excitedwith 'equal rintensity butfwith a phase 'diierence `of 'ninety electrical degrees. "The Imatching -section 2I, `22 :consists of two con,- ductors, each vone quarter 'wavelength (long and of "such 4'diameterrand :spacing that the charac]- t'eristic yirripedanceis the lgeometric mean of the impedance atfpoints I9, `ZIland the characteristic impedance ofthe transmission line comprising Ffeed'ers`23, f2`4; This `matching section therefore provides the "correct termination *for the transmission line 423, 24. The feeder 'system employs the high impedance characteristic of a folded half wave conductor "for insulating purposes. Jumpers 36 fan'dS'I are so located thatitheir centers are one quarter wavelength 'from the Aends of jumpers 32 and 33 thereby forming two folded `half wave elements `which effectively-insulate `jumpers :3'2 `and33 from `the anchorsll, 41,` 48, hand -`69--and ``thatportion pf the conductors between'jumpers 36 and 31 and the anchors. Likewise, jumper 29 is so located that its center is one quarter wavelength from points I9 and 20, thereby forming with conductors 25 and 26 a folded half wave element which insulates points I9 and 29 fro-m the anchors 21 and 28 and from that portion of the conductors between jumper 29 and the anchors. One feature of this antenna system is the symmetrical disposition of the elements which contributes `to the electrical balance of the radiators and feeders, minimizes the electromagnetic coupling between elements, and permits mechanical support of the elements at points of zero voltage without the necessity of insulating material. Furthermore, the 'location of impedance matching and phasing elements being below the reflecting plane, any stray radia-V tion therefrom is effectively prevented from distorting the principal field pattern.

Adjustment of the antenna system described herein is relatively simple. In the embodiment shown in the drawings wherein the feeders 23, 24 are physically and electrically similar, the following procedure is convenient.

nected directly to points I9 and 20. Jumpers 32, 33 are removed and jumpers 36, 31 raised toa point one quarter wavelength below points I9 and 29, thereby insulatingfeeders I1, I8 and radiator II, I3 from the source of'power. -Feeders 2.3, 24 and I5, I6 then constitute aline of uniform characteristic impedance from the source of power to radiator I2, I4. The length of radiator I2, I4 and the spacing between taps of feeders I5, I 6 are then adjusted to effect a termination of said line in its characteristic impedance as evidenced by a minimum of ,standing waves on the line. In the event feeders 23, 24 are different in characteristics from feeders I5, I6, an appropriate matching section is substituted for section ZI, `22 during the above operation. Having completed the impedance matching of .radiator I2, I4, the length of radiatorII, I3 and the spacing of its feeders are made identical with respective dimensions on radiator I2, I4 so that the characteristics of the second radiator are identical with thoseof the first, and the matching section-2l, 22 and jumpers 32, `33 restored to the positions Vindicated in the drawings. Proper phasing is obtained by adjusting the position of jumpers 32, 33 and 36, 31 vuntil uniform response is obtained in a receiving antenna located above the array and rotated in a horizontal plane.

The antenna system describedabove is well -suited for application as a marker for air navigation. When installed with the radiating elements and reflecting plane horizontal, the antenna provides a vertically directed field of relatively narrow limitation as compared With-the fields obtained with more complex arrays. The circular polarization furthermore insures a uniform response in a horizontal aircraft receiving antenna regardless of the orientation of same.

The space contour of eld intensity shownin Fig. 5 illustrates the radiation characteristics of this 'antenna system as determined by actual measurements. The dimensions shown dene the region wherein a positive indication is obtained with the preferred receiver sensitivity and power input tothe antenna. I` claim: i

1. A radio transmitting antenna comprising two straight radiating elementsdisposed in angular relationship; means including matched im- Matching section 2|, 22 is removed and feeders 23, 24 conpedance transmission lines for feeding said elements with radio frequency currents electrically different in phase to effect a rotation of the resultant radiated field; and reflecting means positioned to conne said eld primarily along the normal to said radiating elements. i

2. A radio transmitting antenna comprising va reflecting plane; two crossed half wave elements electrically joined and supported at their centers parallel with and separated no greater than one quarter wavelength from said reflecting plane; and feeder means comprising two matched impedance transmission lines connecting said elements to a common source of power, said transmission lines lbeing of different length thereby effecting a phase difference in the currents in said elements. y l

3. A radio transmitting antenna comprising a pair of crossed wires of equal length, physically at right angles to each other; two pairs of balanced feeder lines symmetrically disposedperpendicular to said wires, said feeder lines being connected to the respective wires equidistant from the centers thereof'and so positioned as to effect the matching of impedances, one of said pair of feeder lines being one quarter wavelength longer than the other pair whereby to feed said wires with currents whose electrical difference of phase angle equals the physical angle of separation of said wires; and reflecting means, said reflecting means and said Wires being located in parallel planes one quarter wavelength apart whereby the Waves Will be reected away `from the reflecting means in a direction primarily perpendicular thereto.

4. A marker beacon radio transmitting antenna system comprising reflective means that is substantially horizontal; a pair of similar straight horizontal doublet antennas which constitute all of the effective radiating elements of the system and are both located near each other and approximately one quarter wavelength above antennas with currents the electrical phase dif- ,ference of which is the same as the mechanical angle of separation.

5. A radio antenna comprising a first straight continuous horizontal wire of n half wavelengths in length, wheren is a whole number; a second straight continuous horizontal wire in substantially the same plane as the rst and of m half wavelengths in length, where m is a whole number; a first pair of feeders for energizing the rst of said wires, said rs't pair of feeders being'respectively connected on opposite sides of the center of the rst wire; a second pair of feedersfor energizing the second wire and respectively connected on opposite sides of the center of the Asec'- ond wire, the second pair of feeders being sulficiently longer than the first pair that the phase difference between-the energizing voltages of Ithe wires equals the physical angle of separation of said Wires; and grounded reflecting means located p quarter wavelengths below theA plane of the wires, where p is an odd whole number.

6. A radio antenna system comprising a *metallic supporting member; a plurality of quarter Wave Aradiating elements extending radially from a common point-on said supporting member' with equal angular displacement; a plurality of feeders symmetrically disposed about and parallel with said supporting member, said feeders being equal `and reflecting means perpendicular to the supporting member and situated between the radiating elements and said electrical means to effect maximum radiation along the axis of` the supporting member awayfrom said reflecting means, and free from influence of said electrical means. 7. A marken beacon antennafor projecting a radio wave vertically upward comprising a central metal supporting post `grounded at its base; a plurality of meta1 antenna elements extending from, connected electrically to, and mechanically "supported by saidpost; said antenna elements extending from said post in the same horizontal plane and at differentphysical angles in such plane, a screen positioned in` a horizontal plane not substantially greater than one quarter wavelength below saidelements; feeder means extending from said antenna elements downward below said screen; and means located below said screen for energizing said feeders with currents having tive antenna` elements whereby a symmetrical r lobe of radio frequency energy is transmitted vertically upward.

8. `A directive marker of theV` rst mentioned feeders to the said additional feeders for therebyA displacing the currents in the third and fourth antenna elements by the `same electrical phase angle as the physical angle of separation of the antenna elements.

9. The device of claim 2 including in addition a central metal supportingpost grounded at its base and electrically connected to and mechanically supportingboth of said half wave elements at their common centers. i

10. A marker beacon antenna comprising a hort izontal reflecting plane, first and second substanz tially straight horizontal antennas positioned at z a physical angle to each other and which are' both located above said reflecting plane by a distance not substantially greater than `one quarter wavelength whereby the energy of the antennas will be radiated primarily upward, firstand second wires symmetrically connected a short distance tending awayfrom said first antenna to consti-` i electrical phase difference angles corresponding to the physical angles of separation of the respec@ beacon antenna system f and supporting structure therefor comprising a s centrally located elongated metal supporting post z rigidly fixed in the ground and extending vertically upward, iirst and second quarter wavelength antenna elements one end of each being mechanicallysupported by and electrically connected lto y the metal supporting post and extending perpendicularly from the post in opposite directions from each other, a horizontal `refiectingscreen located below said `elements and positioned not substantially in excess of one quarter wavelength therei from, symmetrically disposed matched impedance feeders `respectively connected to said first and second elements, said feeders extending substantially vertically downwardly from the elements `and parallel to said post and to a position below said screen, third and" fourth quarter wavelength antenna elements one end of each being` electrically connected to and mechanically supported by said post at substantially the same elevation as said first andsecond elements, said third and fourth elements extending horizontally from said post in opposite directions and at a physical angle to the first and `second `an-` tenna elements, additional symmetrically disposed matched impedance feeders connected to the third and fourth antenna elements respectively and extending substantially Vertically downwardly to a point below said screen, radio frequency-feeding o `meansfor energizing the first mentioned feeders,

and reactance means connecting the lower end off -center ofthe rst of said antennas and extute a matched `impedance feeder therefor, third and fourth wires symmetrically connected to the second of said antennas at points a short distance off center thereof and vextending away from said second antenna to constitute a matched impedance feeder therefor, a first connection electrically joining the outer ends of said first and third wires, a `second connection electrically joining the outer ends of thesecondand fourth wires, a pair of parallel feeders forsupplying radio frequency energy to said first and second connections, and removable matching means cooperating with said pair ofparallel feeders adjacent said connections, said first and second wires being sufficiently longer than the third and fourth to effectuate a phase displacement of the currents in said antennas l corresponding to their physical angles.

11. A `marker beacon antenna as set forth in claim 10 in which the two feeders extend from the `antennas vertically downward below said reflecting plane; said first connection, said second connection, said pair of parallel feeders, and said removable matching means all beinglocated below said refiecting plane.

12. A marker beacon antenna system comprising first and second straight horizontalfradiating elements disposed at a physical angle toeach other andwhich are continuous throughout their respective lengths, matched impedance feeder means including a first Wire connected off center of thefirst of said elements, matched impedance `feeder means` for the second vofsaid elements including a second wire connected off-center of the second element, the first wire being suiciently longerthan` the secondwirethat the phase dis placement of the energizing currentsin the ele ments set up a rotatingiield, radio transmitting z means for energizing said wires, anda reflecting l length below theradiating elements and parallel i thereto. l

plane located not greaterthan one quarter wave- ALBERT D. MARTIN, JR. 

